how to calculate median in Access query using function in VBa - vba

Question

I'm using ms Access query to calculate the MEdian AGe of Patients grouped by Clinic name using Query.
since Access doesn't have build-in Median function. I have to create it using VBA,
I tried many ready functions from web.. but none worked properly. any suggestions for working codes around? could u plz help me to get the median! thank u in advance.

Answer 1

This is a good function also pretty well commented:
Public Function acbDMedian( _
ByVal strField As String, ByVal strDomain As String, _
Optional ByVal strCriteria As String) As Variant
' Purpose:
' To calculate the median value
' for a field in a table or query.
' In:
' strField: The field
' strDomain: The table or query
' strCriteria: An optional WHERE clause to
' apply to the table or query
' Out:
' Return value: The median, if successful;
' otherwise, an error value
Dim db As DAO.Database
Dim rstDomain As DAO.Recordset
Dim strSQL As String
Dim varMedian As Variant
Dim intFieldType As Integer
Dim intRecords As Integer
Const acbcErrAppTypeError = 3169
On Error GoTo HandleErr
Set db = CurrentDb( )
' Initialize the return value.
varMedian = Null
' Build a SQL string for the recordset.
strSQL = "SELECT " & strField
strSQL = strSQL & " FROM " & strDomain
' Use a WHERE clause only if one is passed in.
If Len(strCriteria) > 0 Then
strSQL = strSQL & " WHERE " & strCriteria
End If
strSQL = strSQL & " ORDER BY " & strField
Set rstDomain = db.OpenRecordset(strSQL, dbOpenSnapshot)
' Check the data type of the median field.
intFieldType = rstDomain.Fields(strField).Type
Select Case intFieldType
Case dbByte, dbInteger, dbLong, dbCurrency, dbSingle, dbDouble, dbDate
' Numeric field.
If Not rstDomain.EOF Then
rstDomain.MoveLast
intRecords = rstDomain.RecordCount
' Start from the first record.
rstDomain.MoveFirst
If (intRecords Mod 2) = 0 Then
' Even number of records. No middle record, so move
' to the record right before the middle.
rstDomain.Move ((intRecords \ 2) - 1)
varMedian = rstDomain.Fields(strField)
' Now move to the next record, the one right after
' the middle.
rstDomain.MoveNext
' Average the two values.
varMedian = (varMedian + rstDomain.Fields(strField)) / 2
' Make sure you return a date, even when averaging
' two dates.
If intFieldType = dbDate And Not IsNull(varMedian) Then
varMedian = CDate(varMedian)
End If
Else
' Odd number of records. Move to the middle record
' and return its value.
rstDomain.Move ((intRecords \ 2))
varMedian = rstDomain.Fields(strField)
End If
Else
' No records; return Null.
varMedian = Null
End If
Case Else
' Nonnumeric field; raise an app error.
Err.Raise acbcErrAppTypeError
End Select
acbDMedian = varMedian
ExitHere:
On Error Resume Next
rstDomain.Close
Set rstDomain = Nothing
Exit Function
HandleErr:
' Return an error value.
acbDMedian = CVErr(Err)
Resume ExitHere
End Function
Source: http://etutorials.org/Microsoft+Products/access/Chapter+6.+Data/Recipe+6.4+Find+the+Median+Value+for+a+Field/